FIG. 1 shows the presently known catalytic reactor with fixed bed. In this catalytic reactor, the heat transfer of the chemical heat released is carried out by the heat transfer element with the cooling tubes, and the coolant is usually cool reacting gas. But the catalyst bed out of the tubes usually employs an axial flow bed layer, the major disadvantages of this reactor are as follow:
(1) The gas cooling tubes have the characteristic with poor efficiency of heat transfer and finite quantity of heat transfer, and the temperature distribution of the catalyst bed layer is not perfect.
(2) The axial-flow resistance is great and the production capacity is restricted.
To intensify the heat transfer capacity of the reactor and improve the temperature distribution of the catalyst bed layer, the cellpacking type of the water cooling reactor (Referring to FIG. 2) is developed zealously in the last 20 years. And obtain some favorable effect, but still many obvious disadvantages are as follow:
(1) The resistance (of the catalyst) in the tubes is so great that it need to increase the number of the tubes and the diameter of the reactor.
(2) The reactors require the better material nature and the thick tube plate with a major diameter, and the manufacture hardness is too great. So it costs much.
(3) The utilization ratio of the catalyst loaded in the reactors is poor and the diameter of catalyst loaded in the reactors is large, and it badly limits the large-scale level of the uniserial production capacity. For example, when the industrial scale increases to the 200,000 ton, the diameter of the reactors for the production of methanol is about 4 m, and the ratio of its high-diameter is always 1-2.5. And it also increases the hardness of its transportation and its fixing.
According to these disadvantages, it develops the cellpacking type of the water-cooling reactor with radial flow in these years to solve the problem of the large resistance (FIGS. 3 and 4). Finally, the reactor resistance is reduced from 0.5 MP to 0.1 MPa, and the ratio of the high-diameter is also increased to 3-8.
Although the cellpacking type of reactor with radial flow solves the problem of resistance, it also causes other problems as follow:
(1) The low resistance of the radial flow causes the oversize vent section, the short flow path, and the extraordinary smallness of the velocity of flow. And it causes the coefficient of heat supplied in the catalyst side out of tubes excessively low, which is only ⅕- 1/20 of the normal value of the axial flow. So the heat transfer efficiency falls down, the quantity of heat is hard to carry away, and part of the catalyst is easy to overheat.
(2) Employing the thick tube plate with a major diameter cannot get rid of the disadvantages of the high cost and the large manufacture hardness.
(3) The loading and unloading of catalyst is difficult.
(4) Because of the low heat transfer efficiency, it requires more cooling tubes. So the availability ratio of the high pressure space is even lower than that of the cellpacking type of the reactor with axial flow.